This invention relates to a wire forming apparatus for torsion springs capable of producing the torsion springs automatically and accurately.
In FIG. 1 is perspectively shown a typical example of a torsion spring 1, which is not subjected to a terminal forming. In order to produce such torsion spring 1, there have been used apparatuses for the production of the torsion spring using a rotatable roller feed system or a reciprocable gripper feed system. In this case, a wire is fed into an arbor portion and inserted between an arbor and a pawl formed in an arbor holder, and thereafter the arbor is rotated only at a required number of revolutions and simultaneously moved toward its axial direction at a predetermined pitch while the wire is subjected to the terminal forming before and after the revolution of the arbor. Thereafter the resulting torsion spring is cut down in a given shape.
In such apparatuses for the production of the torsion spring, the adjustment of the number of revolutions of the arbor in the winding of the wire is carried out by regulating a sliding stroke or a rack bar in a crank slide mechanism, but the winding time is required to be a half cycle of the crank, so that the forming, cutting and feeding time of the wire is restricted to the residual half cycle of the crank. Therefore, when plural tools required for the forming are employed to perform a complicated forming, it is frequently difficult to actuate such tools in a given time and further errors of winding angle and feeding length of the wire may not be ignored due to a clearance of gears, wear of each sliding parts and the like.
Therefore, there have been made various attempts to control the revolution of the arbor by means of an electromagnetic clutch, electromagnetic brake or the like, to shorten the rotating time of the arbor in one cycle, and to use a stepping motor or the like. In any case, the conventional wire forming apparatuses for the production of the torsion spring uses a single driving source for the rotation of the arbor, the axial movement of the arbor and the feeding of the wire, and also adopts a mechanically automatic speed changing mechanism for the axial movement of the arbor during the revolution of the arbor, normally the upward movement thereof. Therefore, serious problems such as slipping and the like are caused.